I personally think adding geohash teleportation ruins bitchat. Mesh networking authenticates both proximity and identity (as someone geographically proximate) using actual physics. Abuse is still possible, but limited to people actually near you, which means you have recourse, or can mute peers without "scaling". High-quality globally-accessible location-based chat *must* be curated, either using web of trust, or by using trusted relays. One possible approach to creating a web of trust tailored to this use case would be to stack web of trust on top of mesh networking with location attestations. In other words, start with some root trusted accounts who are allowed to attest to other users' location (for example businesses known to be located in a particular location). After a certain number of attestations, users gain the ability to make attestations for other users. Attestations might expire after a while to account for people moving from place to place. You'd have to be careful about this, since attestations can be forged. As far as I know there's no way to do non-social "proof of location", although crypto land seems to have tried.